Sunday, 10 April 2016

Java - Modifier Types

Modifiers are keywords that you add to those definitions to change their meanings. Java language has a wide variety of modifiers, including the following −
  • Java Access Control Modifiers
  • Non Access Modifiers
To use a modifier, you include its keyword in the definition of a class, method, or variable. The modifier precedes the rest of the statement, as in the following example.

Example

public class className {
   // ...
}

private boolean myFlag;
static final double weeks = 9.5;
protected static final int BOXWIDTH = 42;

public static void main(String[] arguments) {
   // body of method
}

Access Control Modifiers

Java provides a number of access modifiers to set access levels for classes, variables, methods and constructors. The four access levels are −
  • Visible to the package, the default. No modifiers are needed.
  • Visible to the class only (private).
  • Visible to the world (public).
  • Visible to the package and all subclasses (protected).

Non-Access Modifiers

Java provides a number of non-access modifiers to achieve many other functionality.
  • The static modifier for creating class methods and variables.
  • The final modifier for finalizing the implementations of classes, methods, and variables.
  • The abstract modifier for creating abstract classes and methods.
  • The synchronized and volatile modifiers, which are used for threads.

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